NIEHS Study Identifies Gene for Hydrocephalus in Mice
Scientists at the National Institute of Environmental Health Sciences have identified a gene called RFX4 that is responsible for the birth defect hydrocephalus in mice. Loss of a single copy of this gene in mice leads to a failure of drainage of cerebrospinal fluid from the brain cavity, which causes the skull to swell.
About one child in 2,000 worldwide is afflicted by hydrocephalus. Identification of the mouse gene provides a means for researchers to study the possible genetic origins of this common birth defect in humans.
The gene was discovered when researchers noticed that pups in one line of transgenic mice from a completely different study developed head swelling and neurological abnormalities shortly after birth. The NIEHS research team then cloned the defective gene and found that it was responsible for development of a critical structure in the brain that controls cerebrospinal fluid drainage. All of the mice with the defective gene developed the classic symptoms of hydrocephalus, whereas none of the littermates with the normal gene developed this condition. Although the head-swelling led to rapid neurological deterioration and death in many of the transgenic animals, a number have survived to reproduce and propagate the line.
"Animal models of human diseases are often an invaluable tool for studying the underlying causes of a disease, in this case a severe and common birth defect," Darryl C. Zeldin, M.D., one of the authors of the study said. "Identifying the genetic sources of this birth defect in mice may lead to the development of better treatment or prevention of hydrocephalus in humans."
Dr. Zeldin points out that this study is based on the discovery of the mouse gene and its relationship to development of hydrocephalus in mice. The study also describes the cloning of the human homolog of this gene, but the authors cannot say this gene is associated with hydrocephalus in humans yet.
Dr. Zeldin said, "The RFX gene may or may not be associated with hydrocephalus in humans, but that is where we are going in the future with this project. There are likely many causes for hydrocephalus in humans, both genetic and environmental."
"RFX4 belongs to a family of proteins called transcription factors that control expression of other genes," said Perry J. Blackshear, M.D., D.Phil., a co-author of the study. "Identifying exactly which genes are controlled by RFX4 will be an important next step."
The NIEHS researchers have already begun to look for common defects in the RFX4 gene in humans with hydrocephalus. The ultimate goal of these studies will be to develop screening assays to identify this defect so that patients can be counseled appropriately.
The study appears online at http://dev.biologists.org/
on the web site of the scientific journal Development, and
will appear in an upcoming print issue. The study is authored by
Perry J. Blackshear, M.D., D.Phil. (NIEHS), Joan P. Graves (NIEHS),
Deborah J. Stumpo, Ph.D. (NIEHS), Inma Cobos, Ph.D. (University
of California at San Francisco), John L.R. Rubenstein, M.D., Ph.D.
(University of California at San Francisco) and Darryl C. Zeldin,
For further information on the study, contact either Dr. Zeldin at (919) 541-1169 or Dr. Blackshear at (919) 541-4899.